Simultaneous Determination of Cd, In, Tl and Bi by Isotope Dilution-Internal Standardisation ICP-QMS with Corrections Using Externally Measured MoO+/Mo+ Ratios

A method for the simultaneous determination of Cd with In, Tl and Bi by isotope dilution-internal standardisation (ID-IS) ICP-QMS using the same aliquot for rare earth element and other trace element determinations was developed. Samples mixed with an enriched 149Sm spike were decomposed using a HF-HClO4 mixture, which was evaporated and then diluted with HNO3. After determination of Sm by ID-ICP-QMS and Cd, In, Tl and Bi concentrations were determined using the 149Sm intensity as an internal standard. The interference of MoO+ on Cd+ was corrected using the MoO+/Mo+ ratio separately measured using a Mo standard solution, and the validity of the externally determined oxide-forming ratio correction was evaluated. The MoO+/Mo+ ratios measured using the standard solution and samples were similar to 0.0002 and < 0.002, respectively. Detection limits for Cd, In, Tl and Bi in silicate samples were at levels of < 1 ng g-1 with a total uncertainty of < 7%. Cadmium in the carbonaceous chondrites, Orgueil (CI1), Murchison (CM2) and Allende (CV3) as well as Cd, In, Tl and Bi in the reference materials, JB-2, JB-3, JA-1, JA-2, JA-3, JP-1 (GSJ), BHVO-1, AGV-1, PCC-1 and DTS-1 (USGS) and NIST SRM 610, 612, 614 and 616 were determined to show the applicability of this method.Une methode pour la determination simultanee du Cd avec l'In, le Tl et le Bi par dilution isotopique a standardisation interne (ID-IS) ICP-QMS utilisant le meme aliquot pour la determination des terres rares et d'autres elements traces a ete developpe. Les echantillons melanges avec un ajout (' spike ') enrichi en 149Sm ont ete decomposes en utilisant un melange HF-HClO4, qui a eteevapore et, enfin, dilue avec HNO3. Apres la determination du Sm par ID-ICP-QMS, les concentrations en Cd, In, Tl et Bi ont ete determinees en utilisant l'intensite du 149Sm comme standard interne. L'interference de MoO+ sur Cd+ a ete corrige en utilisant le rapport MoO+/Mo+ mesure separement a l'aide d'une solution de Mo standard, et la validite de cette correction a eteevalue. Les rapports MoO+/Mo+ mesures a l'aide des solutions standards et des echantillons ont ete respectivement d'environ 0.0002 et inferieurs a 0.002. Les limites de detection pour le Cd, l'In, le Tl et le Bi dans les echantillons de silicate ont etea des niveaux inferieurs a 1 ng g-1 avec une incertitude totale inferieure a 7%. Le cadmium dans les chondrites carbonees : Orgueil (CI1), Murchison (CM2) et Allende (CV3) ainsi que le Cd, l'In, le Tl et le Bi dans les materiaux de reference : JB-2, JB-3, JA-1, JA-2, JA-3, JP-1 (GSJ), BHVO-1, AGV-1, PCC-1, DTS-1 (USGS) et NIST SRM 610, 612, 614 et 616 ont ete determines afin de demontrer l'applicabilite de cette methode.